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Email deliverability: understanding why your messages arrive, or not

An email accepted by a server is not necessarily an email that gets read. Between sending and the inbox, several decisions are made: the receiving server can refuse the message, delay it or file it as spam. Those decisions depend on your authentication, your sender reputation, your sending practices and how your recipients react.

The articles in this section help you read those signals. They explain how the SMTP protocol works, the difference between a hard bounce and a soft bounce, what the main error codes mean and which fixes to consider when Gmail rejects mail because of reverse DNS.

They also cover what happens outside DNS: the effect of the complaint rate at Gmail, the weight of list quality in B2B, warming up a new domain or IP, one-click unsubscribe, and separating human, marketing and transactional streams. No recipe guarantees inbox placement, but these guides help you look in the right place.